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Proceedings Paper

The evaluation of four different diffuse radiation correction models applied to shadow ring measurements for Beer Sheva, Israel
Author(s): Avraham I. Kudish; Efim G. Evseev
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Paper Abstract

The measurement of the horizontal diffuse radiation, a priori a straightforward task, is fraught with difficulties. It is possible to measure the diffuse radiation by both direct and indirect methods. The most accurate method is probably the indirect one, which utilizes concurrent measurements of the horizontal global and the normal incidence beam radiation. The disadvantage of this method is the relatively expensive tracking system required for measuring the latter. The diffuse radiation can be measured directly with a pyranometer outfitted with either an occulting disk or shadow ring, which prevent the beam radiation from impinging on the pyranometer sensor. The former method can provide accurate measurements of the diffuse radiation but requires a relatively expensive sun tracking system in the east-west axis. The shadow ring is a stationary device with regard to the east-west axis and blocks the beam radiation component by creating a permanent shadow on the pyranometer sensor. The disadvantage of the shadow ring is that it also blocks a portion of the sky, which necessitates a geometrical correction factor. There is also a need to correct for anisotropic sky conditions. Four correction models have been applied to the data and the results evaluated and ranked.

Paper Details

Date Published: 13 September 2007
PDF: 10 pages
Proc. SPIE 6652, Optical Modeling and Measurements for Solar Energy Systems, 66520B (13 September 2007); doi: 10.1117/12.731555
Show Author Affiliations
Avraham I. Kudish, Ben-Gurion Univ. of the Negev (Israel)
Efim G. Evseev, Ben-Gurion Univ. of the Negev (Israel)

Published in SPIE Proceedings Vol. 6652:
Optical Modeling and Measurements for Solar Energy Systems
Daryl R. Myers, Editor(s)

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